1. Field of the Disclosure
The invention relates to a device for the external fixation of bone fractures, to joint elements for such a device, and to a method for the fixation of bone fractures, in accordance with the preambles of the independent claims.
2. Related Art
An external fixator is a device which is mounted outside the body and which is fixed to the bone via threaded metal rods called pins, for the purpose of external fixation of bone fractures of a patient, and is generally used on open fractures with soft-tissue damage or in cases of multiple injuries. In emergency operations on patients with multiple injuries, it is often necessary to defer the definitive treatment of bone fractures of the extremities, for example of the upper leg or lower leg, until other life-threatening injuries have been treated, so as not to put the life of the patient at risk. After a first reduction of the fracture, the latter is provisionally stabilized using an outer frame, the external fixator. In the case of open fractures, it may also be necessary to stabilize the fracture with an external fixator, since definitive primary treatment of the fracture by means of a plate, screw or nail would increase the danger of a post-operative infection. The subsequent removal of the external fixator and the definitive stabilization of the bone by means of a plate and screws or with nails take place, in the case of open fractures, after a clean wound has been obtained or, in the case of patients with multiple injuries, after a stable state has been achieved.
In what is called a pin fixator, pins, for example Schanz screws or Steinmann nails, are anchored in the bone tissue. Such pins are generally steel pins with standardized dimensions. After the bone fracture has been reduced, the pins are securely connected to one another using a rigid outer frame, which is often composed of interconnected bars or tubes. Alternative forms are the pinless fixator, the ring or halo fixator, and combined devices referred to as hybrid fixators.
When a patient who has suffered a high-degree open fracture (3° b or 3° c) is admitted to an accident and emergency unit, this fracture must not be stabilized directly with a plate or nail. Instead, an external fixator is initially fitted in these cases, and the method of treatment is then changed after a few days. The external fixator is dismantled and definitive osteosynthesis is performed, for example by plate or nail. The fitting of an external fixator is often very time-consuming in the known models, since many screws generally have to be tightened after the fracture has been reduced, and, if the position is unsatisfactory, they have to be undone again to allow correction and then tightened anew. If several corrections of position are needed, this procedure can take a very long time. Since patients admitted in emergency situations with high-degree open fractures are often seriously injured, for example with additional trauma to the chest or abdomen, the initial treatment of the bone fracture should be completed as quickly as possible in order to ensure that the patient can be moved as soon as possible to the intensive care unit. For the reasons set out above, this is not possible with the previous fixator systems. Some designs of external fixators also make anatomical adjustment of the bone fracture fragments difficult, since four or more bone pins have to be oriented on a straight line, which can be made difficult or impossible on account of the pin position. Moreover, the structure of the known fixator systems with bars and tubes is often large and bulky.
A number of fixator systems have been developed that are designed to permit better adaptation of the external fixator to the specific circumstances of a fracture.
DE 10125742 C1 discloses an external fixator in which a series of different individual modules provided with a through-opening are drawn onto a tensioning cable. The various types of individual modules have different lengths and/or contact angles. In addition, special connector elements for bone pins and retaining bars are provided. On a contact face at one side, the individual elements each have four studs, and, on the opposite side, they have four depressions, such that two successive individual modules can be arranged with a form fit and with four different rotation angles with respect to each other. After the fixator has been adjusted, the tensioning cable is tensioned. The individual modules are now also connected to each other with a force fit in the direction of the tensioning cable. Said external fixator permits only a relatively rough adaptation to the anatomical circumstances. Moreover, after the elements have been strung onto the tensioning cable, a fine adjustment to the position of the pins is no longer possible. Provision is also made that the bone screws are screwed into the bone only after the fixator has been set up.
U.S. Pat. No. 5,944,719 discloses an external fixator in which a chain of ball joints and sleeves are tensioned with a tensioning cable and stiffened. A plurality of sleeve elements have pivotable pin-holding devices, with which pins mounted in the bone tissue can be secured on the external fixator. For this purpose, the distal end of the pin has to be connected to the pin-holding devices via a nut. The distance of the fixator from the bone is therefore predefined by the length of the pins, which for this reason can only be short. By virtue of the ball joints, the fixator is movable and its shape can be adapted exactly to the anatomical situation. However, since the position of the holding devices on the fixator is predefined, or the fixator has to be correspondingly prepared when being assembled, said device is suitable in particular for planned operations, but less so for initial treatment under time constraints.
WO 99/20194 A1 discloses a similar device with a chain of ball joints that can be stiffened by means of a tensioning cable. In one embodiment, instead of the ball joint elements equipped with the pin-holding devices, sleeves are used that can be mounted subsequently on the fixator chain and that have pin-holding devices, such that the position of the holding devices can be adapted more quickly to the actual position of the pins.
WO 03/068085 A1 discloses a variant of a fixator with ball joint elements analogous to the abovementioned device, in which fixator the connections between the individual ball joints are fixed and released by means of a quick-clamping lever. This allows the fixator to be constructed in sequence from individual parts on site. However, in this embodiment, the overall shape cannot be adapted so quickly, because a large number of locks first have to be released.